Remote-control positioning circuit



May l5, 19571 M. PErRoFF REMOTE-CONTROL POSITIONING CIRCUIT Filed Sept. 3, 1948 Patented May 15, 1951 UNITED STATES PATENT OFFICE REMOTE-CONTROL POSITIONING CIRCUIT Merlin Petr-off, Lake Bluff, Ill., assignor to Stewart-Warner Corporation, Chicago, Ill., a corporation of Virginia Application September 3, 1948, Serial No. 47,574

1 Claim. l

The present invention relates to a system for remote control position selection. The System is of a type that operates only in response to changes in audio frequency.

An object of the invention is to provide an improved position selecting device which may be remotely controlled to move a rotary selectorswitch cr similar part selectively to predetermined position.

Another object is to provide an improved se lector that can be controlled by predetermined changes in audio frequency.

A further object is to provide an improved selector that will operate automatically upon a change in the frequency of a controlling signal.

A still further objecty is to provide. a selector of a very accurate and closely tuned type so that a denite position is always selected.

Another object is to provide an improved selector which is directly responsive to frequency changesv and does not depend on pulsing circuits o r special wave forms.

Further advantages and objects will become more apparent from the following description of two alternative embodiments,- of this invention.

In the drawings:

Fig. 1 is a schematic diagram of the. sending unit;

Fig. 2 is in part ablock and in part; a schematic circuit diagram of a preferred embodiment of the receiving andselecting unit: and

Fig. 3 is a modification of Fig. 2.r

PreviousA to this invention most of the remote controlled selector units were of a type using; special wave forms or short pulses of energyn to position their selector units,

These involved, complicated and cumbersome systems had the disadvantageA or easily getting, out of alignment so that incorrectv positioningy resulted. The present device. isv sim-ple andv requires comparatively few component parte, minimizing maintenance and: increasing stability.

A typical application and description of the operation of a, remote controlled position selec.-` tion device utilizing the present invention follows. The sending unit may comprise a small.

(Cl. S18- 28) means. The output of the Wien bridge controls the firing of a thyratron which in turn controls a motor. The shaft of the motor adjusts the setting of the Wien bridge to the frequency sent by the sending unit and also moves the part to be positioned, such as a switch to select the desired one of several coils for station selection.

The remote control device consists of two remotely located units, as heretofore described, a sending unit as shown in Fig. l and a receiving unit as shown in Fig. 2 or Fig. 3. The send* ing unit is made up of several well known components including an audio frequency oscillator generator I0, a reactance tube modulator I2, and a radio frequency oscillator generator I4 of any suitable type. The oscillator I5 may be of any well known design, such as an inductancecapacitance, a resistance-capacitance, or a phase shift type. The reactance tube modulator I2 may be of the type commonly used for producing a frequency modulated Wave in FM transmitters. It will be understood that the use of a FM system is not essential, although it is usually preferable to the use of an AM or pulsed system if a line is not available as the meansk for transmittingy the audio frequency signals from the sending unit toy the receiving unit.

The tuning circuit I5 of the oscillator IU may comprise an impedance I6- shown as an inductance coil, a capacitance I8, and a group of capacitors 2li which may be connected in parallel with the capacitance I by selective operation of 'switches 22. It is to be understood that the capacitors I8 and 2Q and the inductance IS are intended to be representative of any other impedances of impedance meshes whereby the fre quencyy of the oscillator Iii may be adjusted in discrete steps. By selective connection of the impedances 20 in the tuned circuitl I5 its resonant frequency, and hence the audiov frequency output of the generator, may be changed. This adjustable audio frequency signal is supplied to the input circuit of the reactance tube modulator circuit I2 tor change the eifective reactance of by a radio frequency amplifier 32 of any well known construction and fed into a discriminator and audio frequency amplifier 34 which acts to separate the original adjustable audio frequency signal from generator I and the fixed radio frequency generated by the R. F. generator i4 and to amplify the audio frequency.

The amplified audio wave which is of the identical frequency as that selected and supplied by the sending device is directly coupled to a primary 38 of a coupling transformer 38 by conductors 40 and 42. The secondary 44 of the coupling transfer 38 is connected by conductors 58 and 52 to the input terminals 48 and 48 of a Wien bridge. The Wien bridge is made up of fixed resistances 54 and 56 in two of its legs and the standard arrangement of a capacitance 58 in series with a variable resistance 60 in a third leg and a capacitance 02 in parallel with a variable resistance 84 on the fourth leg. The bridge has a grounded output terminal 66 between the Variable resistances and has its other output terminal 10 between the fixed resistances 54 and 58 connected by conductor 88 to a plate 'l2 of a diode 14.

The cathode T8 of the diode 74 is connected to the grid 80 of a normally nonconducting thyratron 82 by a capacitor input pi section filter. The input and output capacitors 84 and 88 of the filter `|8 are grounded. Between the ungrounded terminals of the capacitors 84 and 88 is a resistor 88. This fixed resistor 88 connects the cathode 'i0 to the grid 30. A high value grid return resistor 89 connects the grid 80 to ground.

In the thyratron 82 the cathode 90 and the screen grid 92 are grounded. The plate S4 is connected by a conductor 98 to one terminal 9'! of a field coil 98 of a motor 99 that operates effectively on half wave power. The other terminal |00 of the field coil 98 is supplied with 60 cycle A. C. power through line |02. The other side of the A. C. `power supply is grounded, thus completing the plate circuit of the thyratron 82.

The motor 99 has a rotor |04 on a shaft |08. One end of the shaft |06 is connected to conductive positioning contact arms |08 and ||0 which vary the resistances 60 and 84, respectively. The connection between the shaft |08 and the arms |08 and ||0 is grounded and therefore the portion of the resistance B0 or 64 that is between one of the arms |08 or ||0 and ground is eiiectively shorted out. Also mounted upon the shaft |08 is position selector ||2. This selector may be for the purpose of selecting pretuned coils for present station changes on a radio receiver or some similar function.

The operation of this section of the receiving unit is as follows: In normal position the output of the Wien bridge is zero and thus no energy is supplied by means of the diode 'i4 to the grid 80 of the thyratron 82. The thyratron will be nonconducting and thus no power will be sent through the coils 98 to position the motor rotor |04. When a new position of selector ||2 is desired another switch 22 or group of switches 22 is closed or opened, thus transmitting a new frequency. This new audio frequency when picked up by the Wien bridge, which is at that time set for the old frequency, will develop a voltage across points l0 and 66. The diode 14 will pass a half wave portion of this voltage. The filter 13 will smooth this half wave to a rippling direct current rand the grid 80 of thyratron 82 will be biased to its firing voltage. The A. C. voltage in the plate circuit of the thyratron 82 will iiow in the coils 98 each half cycle and thus rotate the rotor |04. The rotor |04 will move the resistor arms |08 and ||0 to adjust the Wien bridge to a position where no voltage will be present at point 'l0 and the rotor |04 will stop because the thyratron 82 will cease conducting. At this time the Wien bridge is tuned to the new audio frequency. The selector 2 will, because of the movement of rotor |04, have selected the desired position or performed its desired function.

As can be readily understood the resistor arms |08 and ||0 and the selector switch ||2 must necessarily be of a type that will permit continuous rotation as the motor will always rotate in one direction.

The modification of the receiving unit as shown in Fig. 3 is the same as that of Fig. 2 except in the detail of the balancing circuit. In this case a balancing unit of the T null type is used and the construction and operation of this circuit is all that needs further explanation. Similar parts have been numbered with the same numbers as appear in Fig. 2.

The T circuit consists of two common T sections. The first T section is composed of a pair of variable resistances |20 and |22 in series having the mid point |24 grounded through capacitor |28. The other T is composed of the condensers |28 and |30 in series and having the point |32 connecting them grounded through variable resistor |34. The series resistors |20 and i22, paralleled by the series capacitors |28 and |30, complete a circuit from the audio amplifier 34 through line |36 to the plate 'i2 of the diode 14. The variable resistors |28 and |22 are varied simultaneously and the same amount. Arms connected to the shaft |08 supporting the rotor |04 vary the resistor |34 and the resistors |20 and |22 when a change in frequency is detected by the discriminator 34 until a zero output at the plate 'I2 is once again effected. This operation is very similar to that of the resistors 00 and B4 in Fig. 2 and controls the output circuit in the same manner.

While but one embodiment and a modification of this embodiment have been described, it should be understood that the details thereof are not intended to limit the invention except in so far as is set forth in the accompanying claim.

Having thus described my invention, what I claim as new and useful and desire to secure by Letters Patent of the United States is:

In an apparatus for moving a member to different predetermined positions in response to electrical signals of different audio frequencies received from a remote control station, the combination of a null network having a transmission null at one audio frequency, the network having a control element which is variable to change the frequency of the transmission` null; means for impressing the signals received from the control station upon the null network; a thyratron having an anode, a cathode and a control grid; a rectifier connecting the output of the network with the grid of the thyratron to furnish positively polarized signals to the grid in response to signals from the network for rendering the thyratron conductive; a source of alternating current power; an electric motor connected in series with the source and the anode and cathode of the thyratron, the motor being energized when the thyratron is conductive; means for connecting the motor with the member to move the latter; and means connecting the motor with the controll element of the network for adjusting the latter to a null.

MERLIN PETROFF.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number 

